Some devices provide a sensory feedback to the human user or operator so that the operator has confidence that the operation sought by the operator has been properly registered. Such is the case, for example, for some computer input devices, such as a mouse or other pointer device which provides a clicking sensation when depressed or operated. By contrast, some input devices, such as a touch screen, for example, do not provide such a click or sensory confirmation. For that reason, it has been proposed to use haptic technology so that, upon human input, a touch screen vibrates in order to provide the confirmatory feedback to the user that the touch screen is receptive to the input. In general, “haptics” is a field of technology which takes advantage of the sense of touch by applying forces, vibrations, or motions to the user.
FIG. 13 shows an example haptic actuator wherein a moveable member (depicted by horizontal hatching when viewed in landscape) is resiliently attached to a stationary member (having vertical hatching) both by two spring members (spaced apart in the horizontal direction) and two pole member-carrying subcomponents (spaced apart in the vertical direction). One of the pole member-carrying subcomponents is shown in FIG. 13A at a time when a coil carried by one of the pole members is not energized, and is shown in FIG. 13B at a time when the coil is energized. A resilient, springy frame or perimeter of each pole member-carrying subcomponent has one opposing side thereof attached by two fasteners (depicted by circles) to the stationary member and another opposing side attached by similar two fasteners to the moveable member. The two pole members of each subcomponent are attached to the subcomponent frame by connecting arms. When the coil is not energized, the frame of each pole member-carrying subcomponent has a rectangular shape, as shown in FIG. 13A. But when the coil is energized, the pole members are attracted toward one another and the springy, resilient frame distorts (e.g., in a direction depicted by the arrow in FIG. 13B) into a non-rectangular, parallelogram shape.
Each pole member-carrying subcomponent may be fabricated to provide a specified gap size between the two pole members. But if fastening of a pole member-carrying subcomponent (to the stationary member or the moveable member) is not accurate, the springy frame of the pole member-carrying subcomponent may be pre-distorted, adversely affecting the non-energized initial gap size.
Thus, the two pole member-carrying subcomponents of the device of FIG. 13 effectively provide a measure of suspension in addition to the two horizontally spaced spring members. The suspension provided by the two pole member-carrying subcomponents may cause interference and adds unpredictability to performance (e.g., to initial gap size, as explained above). The greater the number of parts, the greater is the potential of unintended interference. Measured attributes such as displacement and acceleration levels become highly variable from one manufactured unit to others, thereby compromising quality and user satisfaction.
FIG. 14 illustrates a haptic actuator known as the “A300”. The A300 haptic actuator is an intermediate device which is situated between an unillustrated stationary member and an unillustrated moveable member (e.g., which may carry a user input device). The A300 haptic actuator comprises an actuator frame 179 or housing which surrounds both a first pole piece 180 and a second pole piece 182. In the A300 actuator first pole piece 180 (with the electromagnetic coil 184 around it) is rigidly attached to the actuator housing 179, which is then rigidly attached to the unillustrated stationary member. An elongated U-shaped spring 187 connects second pole piece 182 to the actuator housing 179, the second pole piece 182 being carried in an internal channel of spring 187. A gap 191 exists between the first pole piece 180 and the second pole piece 182. In a direction parallel to the gap the spring 187 has an internal channel including a channel mouth oriented toward first pole piece 180 and coil 184. The second pole piece 182 fits into the channel mouth. A backside of spring 187 opposite the channel mouth is connected to an assembly 185 that is in turn connected to the unillustrated moveable member.
Prior art haptic devices, such as those of FIG. 13 and FIG. 14, rely on separate and distinct actuator units, carrying two pole pieces, mounted intermediate a stationary member and a moveable member to provide the haptic effect. These actuator units are limited to approximately 300 microns of actuation travel, so the assembly of the actuator unit to both the stationary member and to the moveable member must be precise. Furthermore, due to inefficiencies, several actuator units are typically needed for each assembly. These actuator units typically include a spring to drive the second pole piece and some type of housing to locate the two pole pieces relative to each other within the actuator unit.